REFLECTOR: Something for Nothing? Never

[Alan Shaw <wingco@iu.net>]

HYTEC

>  10.5:1 pistons.

My experience with high compression pistons on the prototype was unpleasent.

Hard to hot start and fast rough idle.   This was before we had electronic
ignition or CS props.  The fast idle wore out brakes in taxi and made landing
with fixed prop and gear almost impossible unless you shut the engine down on
final, but it did that on it's own sometimes anyway.
Don George recomends steel cylinders, no porting and standard pistons for max
power in the long run.  He's not real happy with our electronic ignition but
getting use to it.

Maybe you have someone out there who can tame the high compression four cylinder
beast but personally I prefer a light 235 hp 540 turning a smooth quite 2400 rpm
max.  A 275 hp 540 has 180 hp at 10,000' while a 200 hp 360 has a little over 100
hp at that altitude.  Since a Velocity has a long thick turbulent flow wing the
only way to go fast is up high but you need horses left up there to do it.  The
only way to really get horses at altitude is large displacement, turbo or
supercharging.

I have flown the 300hp 173 full aft stick solo.  It had one small auto plus an
aircraft battery in the nose and a 180" canard not counting the big tips.  It
bucked more than usual but did not depart. I strongly recommend that the 405 lb
parallel valve 260+ hp be used instead of the 455 lb 300 hp.  Because of balance
this plane lands very sweet compared to it's four cylinder counter part.
Take-off & climb....well you know it's a 540!

We can get rid of one battery and use a CS prop if the canard is down sized to
170" to 175" depending on the pilot weight but now we are really re-designing the
airplane to the extent that the gear has to be rotated back 2" so it won't fall
on it's tail.  Ya'll (excuse me I'm from the south) have to understand that we
are juggling three very important numbers here:  center of gravity, center of
lift and center of rotation.
Now if everybody starts cutting and changing their airplanes this way and that we
are going to have a bunch of test pilots and someone is going to get hurt.  I
don't know what to do about it though because everybody wants performance.  Maybe
if we communicate our intentions then we can help keep each other out of trouble.

In my opinion, the cg and Vne problems associated with putting 540's on small
airplanes are not near as dangerous as working with reduction units, water
cooling systems, new induction systems and new props.  CG, center of lift and
structural calculations are straight forward math.

Alan Shaw